Manufacturing should always be considered during product design. Preferably, it should be discussed with the team or supplier who will make the part. Skipping or rushing this part of the development process leads to parts that cost more than they should.

Casting processes are an economical way of producing parts in small to very large quantities as they minimize material usage and machining operations. This blog reviews what’s involved in bringing the design of a metal part to fruition by casting and highlights the major decisions needed along the way.

8 Steps on the Journey

Many casting buyers have detailed requirements for part design and approval. The automotive industry for example, uses the formal Production Part Approval Process (PPAP). This requires the vendor or foundry to demonstrate their ability to produce and supply the parts needed at the required quality and production rate.

In broad terms, the steps involved in moving from a concept to a physical metal part are:

1. Concept design
2. Process selection
3. Material selection
4. Detail design
5. Tooling design and manufacture
6. Sample production
7. Inspection and approval
8. Full production

Here’s a look at each.

Concept Design

This is where the functional needs are explored and a solution developed. A physical prototype might be produced to check for fit and appearance.

Process Selection

There are many ways to cast a part. Sand casting is often the default choice because it has good economics for small to large quantities, tooling costs are relatively low, and lead times are short. When higher precision is needed, and especially if the part has a lot of fine detail and tight tolerances, investment casting may be a better choice, despite higher tooling costs and longer lead time.

Material Selection

When the application permits, select an alloy with good castability or fluidity. (Nonferrous alloys generally perform better than steels.) This will reduce defect rates and permit casting of thin walls and sections.

Detail Design

Once the process and alloy are known, the design is refined to accommodate specific process requirements. For example, sand casting needs draft angles on vertical surfaces to let the pattern release smoothly from the mold. There will also be a parting line where the two halves of the mold meet, and the design team may want to consider where this should go.

Tooling Design and Manufacture

Sand casting uses patterns to create the mold cavity. To save time and money, these may initially be made from wood, but for larger quantity production, aluminum or other metal is often used.

Investment casting patterns are molded in wax. For initial samples these can be CNC machined but large quantity production requires injection-molded patterns.

Tooling design also includes the runners, risers and gates that will feed metal into the mold cavity. These are critical elements because how the mold fills affects part quality, defect rates and cycle time.

3D printing offers a new capability in tooling manufacture. Sand molds can now be – slowly – printed, rather than needing a pattern. Likewise, wax patterns for investment casting can also be printed.

Sample Production

An initial production run will confirm that the tooling is correct. The parts produced can be used for testing or sales demonstrations. Customers often like to see a sample before committing to production tooling.

Inspection and Approval

First Article Inspection (FIA) verifies the parts being cast meet all requirements. If any deficiencies are discovered, this information is used to modify tooling or process parameters.

Full Production

Only after the customer has signed-off to say the parts being cast meet their requirements can production begin.

Let Impro be Your Partner For Quality Metal Castings

Casting produces near-net shape metal parts that need little machining. Achieving consistent results requires careful attention to both part and tooling design, and a lot of experience.

Impro uses both sand casting and investment casting to produce quality metal parts. Our processes and the products we deliver meet the expectations of customers in aerospace, automotive, industrial and other industries. If you need a dependable source of metal castings, contact us.